The major emphasis of this research program will focus on studies of the ocular physiology of the teleost. The primary area of investigation is oxygen toxicity, both studies of protection against O2 toxicity by the enzyme superoxide dismutase and the identification of the physiological targets for the superoxide anion. Studies have indicated that exposure of retinas to hyperbaric oxygen may result in significant decrease in Na-K ATPase activity. Ocular tissues normally exposed to elevated oxygen tensions (rainbow trout retina) are found to be resistant to oxygen toxicity. We have developed an assay suitable for use on crude tissue homogenates for superoxide dismutase which will be applied to a variety of species to determine if a positive correlation exists between intraretinal oxygen tensions and enzyme activity. We plan to investigate the relative sensitivity of retinal cells to oxygen toxicity by use of intracellular electrophysiological recording techniques.